Members of the emergency services work next to a tram after it overturned injuring and trapping some passengers in Croydon (Picture: Reuters)

Mayor of London Sadiq Khan talking with (L to R) deputy director of operations for London Ambulance Peter McKenna, British Transport Police Chief Constance Paul Crowther and Director of operations for London Fire Brigade Dany Cotton, at the scene in Croydon (Picture: PA)

Robin Smith, Assistant Chief Constable of the British Transport Police, confirmed they are investigating whether the driver fell asleep, alongside ‘a number of factors’.

He said officers would be ‘working through the night’ at the scene, and staff would be present for a ‘number of days’.

He said: ‘We have a very difficult and very challenging scene. We have carriages that are lying on their side – very heavy, 300 tonnes worth – which will eventually have to be moved carefully.

‘And at the same time, us being able to understand exactly what happened.’

Members of an investigation team at the scene where a tram derailed near Sandilands tram station in Croydon (Picture: LNP)